Coupler for a stereo phonograph cartridge



Dec. 27, 1966 R. DALLY ETAL 3,294,925

COUPLER FOR A STEREO PHONOGRAPH CARTRIDGE Original Filed July 30, 1962 2 Sheets-Sheet l INVENTORSI ROY DALLY, WILLIAM A. CAVAGNARO,

THEIR ATTORNEY.

Dec. 27, 1966 R. DALLY ETAL 3,294,925

COUPLER FOR A STEREO PHONOGRAPH CARTRIDGE Original Filed July 30, 1962 2 Sheets-Sheet 2 FIG.8. FIG.9.

\ INVENTORS: ROY DALLY, WILLIAM A. CAVAGNARO,

% BY W e, M

THEIR ATTORNEY.

United States Patent 3,294,925 COUPLER FOR A STEREO PHONGGRAPH CARTRIDGE Roy Dally, Warrensburg, Ill., and William A. Cavagnaro, Greece, N.Y., assignors to General Electric Company, a corporation of New York Continuation of application Ser. No. 213,352, July 30,

1962. This application May 13, 1965, Ser. No. 459,512 3 Claims. (Cl. 179-10041) This invention relates to stereo phonograph pickup cartridges such as the type having ceramic transducer elements, and particularly relates to a coupler for mechanically coupling transducer elements to a drive rod which is provided with a needle or stylus for engaging the groove of a phonograph record.

The present invention is a continuation of my copending application Serial No. 213,352, filed July 30, 1962, now abandoned, for Coupler for a Stereo Phonograph Cartridge.

A well known type of stereo phonograph cartridge employs a pair of elongated ceramic transducer elements arranged mutually parallel within a housing. A drive rod, provided with a stylus at the front end thereof, is positioned symmetrically below and parallel to the transducer elements. A V-shaped coupler, usually made of plastic, mechanically intercouples the drive rod and the ceramic elements. The apex of the coupler engages against the drive rod, and the ends of the coupler are respectively connected to ends of the transducer elements. The remaining ends of the transducer elements, and the rear end of the drive rod, are suitably attached to the cartridge housing.

The coupler is a vital link between the drive rod and the transducer elements, and its characteristics have a great effect on the performance and durability of the pickup cartridge.

An object of the invention is to provide an improved coupler for phonograph pickup cartridges.

Another object is to provide a phonograph cartridge coupler for achieving improvements in performance characteristics such as frequency response, compliance, damping, distortion, resonance, energy transfer, and shock absorption.

Further objects will be apparent from the following description and claims, and from the drawing in which:

FIG. 1 is a side view of a phonograph pickup cartridge in accordance with a preferred embodiment of the invention;

FIG. 2 is a front view of FIG. 1;

FIG. 3 is a bottom view of FIG. 1;

FIG. 4 is a cross-sectional view taken on the line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken on the line 55 of FIG. 4;

FIG. 6 is a front view of a preferred embodiment of the coupler in accordance with the invention;

FIG. 7 is a side view of FIG. 6;

FIG. 8 is a front view of an alternative embodiment of the invention; and

FIG. 9 is a side view of FIG. 8.

The coupler of the invention comprises, basically and in its preferred embodiment, a V-shaped member made from rubber-like material such as butyl and shaped to have tapered legs. The coupler is provided with openings for receiving transducer elements and also a drive rod, whereby the coupler material completely surrounds and is in intimate engagement not only with the transducer elements but also with the drive rod.

The ceramic stereo pickup cartridge shown in the drawing comprises a housing 11 which may be composed of an upper part 12 and a lower part 13 attached together by means of rivets 14. The interior of the housing 11 is partly hollow, and contains a pair of elongated ceramic transducer elements 16 and 17, arranged mutually parallel and with the sides thereof inclined oppositely at 45 degree angles, and anchored to the housing 11 at the rear ends thereof by suitable means such as resilient blocks 18. The transducer elements 16 and 17 preferably are in the shape of flat bars, as shown, and are pro vided with metallic electrodes (not shown) deposited or attached to their flat side surfaces, and suitable connecting wires (not shown) extend from these electrodes to terminal pins 2124 at the rear of the cartridge housing 11.

A stylus assembly 26 comprises a barrel member 27 seated at the underside of the housing 11, and adapted to rotate degrees about an axis parallel to the general axis of the housing 11. The barrel 27 is manually rorated by means of a lever arm 28 which eXtends laterally therefrom and is long enough to extend beyond the sides of the housing 11. The barrel 27 is flattened at opposite sides thereof as indicated at '31 and 32, and a spring clip 33 is arranged to ride against the barrel 27 so as to engage against the flattened portions 31, 32 alternatively when the barrel 27 is at the two extremes of its 180 degree rotation as determined by which side of the housing 11 the lever arm 28 extends from.

An elongated drive rod or tube 36 is concentric with, carried by, and extends axially forward of the barrel 27, as shown. The front end of the drive rod 36 is provided with two styli 37 and 38, arranged on opposite sides of the drive rod 36 and extending laterally therefrom, so that when the barrel 27 is in one of its two extreme positions, one of the styli 37 will extend downwardly, and when the barrel 27 is in its other extreme position, the other stylus 38 will extend downwardly. Thus, the two extreme rotary positions of the stylus assembly, are two operating positions in which one or the other of the styli is in record-playing position. A convenient way to attach the styli 37, 38 to the drive rod 36, is to flatten the front end of the drive rod 36, as shown, and drill holes at suitable angles into the flattened front end of the drive rod into which the styli 37, 38 may be inserted and held by means of an adhesive or cement.

A coupler 41, to which the present invention is directed, is generally V-shaped to provide two legs 43, 44 which are perpendicular with respect to each other. The ends of the legs 43, 44 are enlarged, as shown at 45 and 46, and are provided with suitable rectangular openings therethrough to fit snugly around the forward ends of the ceramic transducer elements 16, 17. The legs 43, 44 are of equal length and each is at a 45 degree angle with respect to the plane in which the elements 16 and 17 lie; this plane is horizontal when the cartridge is in normal operating position. The apex or bottom of the coupler 41 is enlarged, as shown at 47, and is provided with a circular opening 48 through which the drive rod 36 extends and is rotatable when the barrel 27 is rotated to change needles. The drive rod opening through the coupler 41 is of such a size so that the drive rod 36 fits snugly therein, so that the drive rod 36 is in close mechanical contact with the apex of the coupler 41. A slit or slot 42 is provided at the enlarged apex 47 of the coupler 41, between the drive rod opening and the lower extremity of the coupler. This slit extends in a vertical plane parallel to the drive rod 36, and is for the purpose of enabling insertion and removal of the drive rod into and from the coupler, by readily forcing the drive rod through the slit 42, when the stylus assembly 26 is installed or replaced. If desired, the slit 42 may be given some width, so as to be a slot.

The two legs 43, 44 of the coupler are tapered, as shown, as will be more fully described.

The coupler 41 preferably is made from a rubber-like material; i.e., a material that is highly resilient and readily deformable and has a rapid and complete restoring force so that it will quickly return to its original shape upon being deformed and then released. Butyl, having a Shor e A durometer hardness range of from about 35 to 55, is a suitable rubber-like material, as is rubber itself. Due to the relatively great pliability of this material, the drive rod 36 may be easily inserted into the drive rod opening of the coupler, by pushing it through the slit 42; when so doing, the material of the coupler flexes readily and spreads apart to form a temporary gap at the slit 42, to accommodate the drive rod 36. Thus, removal and replacement of the stylus assembly 26 is easily accomplished, while at the same time the drive rod 36 will be substantially completely surrounded by, and will be in' good mechanical engagement with, the coupler 41 so that vibrations thereof, when one of the styli 37, 38 engages the groove of a rotating phonograph record, will be faithfully transmitted along the legs 43, 44 of the coupler 41, to the transducer elements 16, 17. In order that the drive rod 36 will vibrate properly, the rear end thereof is attached to the barrel 27 in a resilient manner, as by being imbedded in a resilient material such as rubber contained in the forward portion of the barrel 27, in a well-known manner.

When the pickup cartridge is used to play a stereophonic record of the type having two stereophonically related signals recorded on the separate walls of the groove, the grooves being at a mutual 90 degree angle and each groove being at a 45 degree angle with respect to the vertical, undulations of one side of the groove will vibrate the drive rod 36 in a direction along the axis of the coupler leg 43, and undulations of the other wall of the record groove will vibrate the drive rod 36 in a direction along the axis of the coupler leg 44; thus, the mechanical undulations of the record grooves will respectively vibrate the different ceramic elements 16 and 17 due to the functioning of the coupler 41.

It is found that the legs 43, 44 of the coupler 41, being tapered as shown, and in accordance with the invention, are considerably stronger in their axial directions, and resist buckling or bending when in use, as compared with prior-art couplers having straight-sided legs. The in1- proved operational rigidity of the coupler legs, provided by the tapering thereof, reduces distortion in the process of mechanically coupling vibrations of the drive rod 36 to the transducers 16 and 17, and also reduces the likelihood of being self-resonant at any particular frequency, thereby reducing undesirable effects of self-resonance of the coupler 41, and also providing a wider range of frequency response for the pickup cartridge. Also, the tapered legs enable the coupler to be lighter in weight, which improves the compliance and the high-frequency response, and enable the use of soft and pliable material for the coupler.

The coupler of the invention, being made of a softer and more pliable material than the relatively stiffer priorart couplers, achieves improved damping characteristics on the drive rod 36, and absorbs the mechanical shock of any sudden impact on the drive rod 36, thereby protecting the fragile ceramic elements 16 and 17 from being broken or damaged by sudden shock as might be caused by dropping a tone arm, containing the cartridge, onto the surface of a record or turntable.

In accordance with the invention, the drive rod opening 48 in the coupler 41, substantially completely surrounds and is in good engagement with, the drive rod 36, thereby increasing energy transfer between the drive rod and the ceramic elements 16 and 17, as compared with prior-art couplers which are provided with an inverted V-shaped notch at the apex thereof whereby the drive rod merely rests against the apex of this notch.

FIGS. 6 and 7 show the coupler 41 d-isassociated from a pickup cartridge, the openings therethrough for the ceramic elements being designated as 16' and 17. In a preferred embodiment of the invention, the taper of the legs 43 and 44 is in a direction, on each leg, so that the legs are narrowest at the ends thereof toward the drive rod opening 48, and are relatively widest at the ends thereof respectively toward the transducer element openings 16' and 17.

In the modification shown in FIGS. 8 and 9, the taper of the coupler legs is reversed, and these legs having reversed tapers are respectively indicated by the numerals 43 and 44'. It is the essence of the invention that the legs be tapered, and the particular direction of taper, i.e., as shown in FIGS. 6 and 7, or as shown in FIGS. 8 and 9, will depend upon cartridge design criteria such as the desired point of mass center and the decoupling point, these factors being design criteria well known to those skilled in the art of designing pickup cartridges. Either direction of taper will accomplish the desired objectives of reducing the weight of the coupler, strengthening the coupler legs, and reducing the tendency for these legs to resonate at any particular frequency.

While preferred embodiments of the invention have been shown and described, various other embodiments and modifications thereof will be apparent to those skilled in the art and will fall within the scope of invention as defined in the following claims.

What we claim is:

1. In a stereo phonograph pickup cartridge having a pair of transducer elements and an elongated drive rod positioned in spaced relationship with respect to the transducer elements, an improved coupler for connection between the drive rod and transducer elements, comprising a V-shaped member made from a rubber-like material, means attaching the legs of said member to said transducer elements, respectively, and an opening through said member at the apex thereof, said opening being formed by a continuous internal wall of said member, a slit formed in the apex of said member between the exterior of said apex and the internal wall of said opening thereby to allow said drive rod to be inserted in said opening and resiliently entrapped therein by being passed through said slit, said slit including a pair of contiguous walls in at least partially engaged disposition thereby to close said opening from the exterior of said apex, said drive rod being normally extended through said opening, perimetrically surrounded by and in engagement with the wall of said member, and the legs of said member being tapered between the drive rod and the transducer elements, said member being arranged as a free floating connection between said drive rod and said transducer elements thereby to resiliently couple said drive rod to said transducer elements and improve the efficiency of said coupler.

2. A coupler for free floating connection between a drive rod and a pair of transducer elements of a phonograph pickup cartridge, comprising a V-shaped member made from a rubber-like material, said member including a pair of tapered legs arranged in substantially perpendicular relationship and connected to each other at an enlarged apex, a first opening through said member at the apex thereof to accommodate said drive rod, said first opening being formed by a continuous internal wall of said member for perimetrically surrounding and engaging a drive rod received therein, a slit formed in said member between the interior wall of said first opening and the extenior of said apex thereby to allow said drive rod to be inserted in said opening and resiliently entrapped therein by being passed through said slit, said slit including a pair of contiguous resiliently engaged walls thereby to positively close said first opening from the exterior wall of said apex and second and third openings through said member adjacent the free ends of the legs thereof to accommodate said transducer elements, respectively, said legs being tapered between the drive rod opening and the transducer element openings.

3. A coupler for free floating connection between a drive rod and a pair of transducer elements of a phonograph pickup cartridge, comprising a V-shaped member made from butyl rubber material having a Shore A durometer hardness range of from 35 to 55, said member including a pair of tapered legs arranged in substantially perpendicular relationship and connected to each other at an enlarged apex, a first opening through said member at the apex thereof to accommodate said drive rod, said first opening being formed by a continuous internal wall of said member for perimetrically surrounding and engaging a drive rod received therein, a slit formed in said member between the interior wall of said first opening and the exterior of said apex thereby to allow said drive rod to be inserted in said opening and resiliently entrapped therein by being passed through said slit, said slit including a pair of contiguous resiliently engaged walls thereby to positively close said first opening from the exterior wall of said apex and second and third openings through said member adjacent the free ends of the legs thereof to accommodate said transducer elements, respectively, said legs being tapered between the drive rod opening and the transducer element openings.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Ahrens et a1.: German application No. 1,107,956, published May 1961.

Product Design Catalog File, New York, Sweets Catalog Service, a Division of F. W. Dodge Corp. 1961. Section 3a/Dup., pp. 2-3.

NORTON ANSHER, Primary Examiner.

EVON C. BLUNK, Examiner.

WILLIAM E. JACKSON, J. F. PETERS, JR.,

Assistant Examiners. 

1. IN A STERO PHONOGRAPH PICKUP CARTRIDGE HAVING A PAIR OF TRANSDUCER ELEMENTS AND AN ELONGATED DRIVE ROD POSITIONED IN SPACED RELATIONSHIP WITH RESPECT TO THE TRANSDUCER ELEMENTS, AN IMPROVED COUPLER FOR CONNECTION BETWEEN THE DRIVE ROD AND TRANSDUECE ELEMENTS, COMPRISING A V-SHAPED MEMBER MADE FROM A RUBBER-LIKE MATERIAL, MEANS ATTACHING THE LEGS OF SAID MEMBER TO SAID TRANSDUCER ELEMENTS, RESPECTIVELY, AND AN OPENING THROUGH SAID MEMBR AT THE APEX THEREOF, SAID OPENING BEING FORMED BY A CONTINUOUS INTERNAL WALL OF SAID MEMBER, A SLIT FORMED IN THE APEX OF SAID MEMBER BETWEEN THE EXTERIOR OF SAID APEX AND THE INTERNAL WALL OF SAID OPENING THEREBY TO ALLOW SAID DRIVE ROD TO BE INSERTED IN SAID OPENING AND RESILIENTLY ENTRAPPED THEREIN BY BEING PASSED THROUGH SAID SLIT, SAID SLIT INCLUDING A PAIR OF CONTIGUOUS WALLS IN AT LEAST PARTIALLY ENGAGED DISPOSITION THEREBY TO CLOSE SAID OPENING FROM THE EXTERIOR OF SAID APEX, SAID DRIVE ROD BEING NORMALLY EXTENDED THROUGH SAID OPENING, PERIMETRICALLY SURROUNDED BY AND IN ENGAGEMENT WITH THE WALL OF SAID MEMBER, AND THE LEGS OF SAID MEMBER BEING TAPERED BETWEEN THE DRIVE ROD AND THE TRANSDUCER ELEMENTS, SAID MEMBER BEING ARRANGED AS A FREE FLOATING CONNECTING BETWEEN SAID DRIVE ROD AND SAID TRANSDUCER ELEMENTS THEREBY TO RESILIENTLY COUPLE SAID DRIVE ROD TO SAID TRANSDUCER ELEMENTS AND IMPROVE THE EFFICIENCY OF SAID COUPLER. 